U.S. patent application number 12/640863 was filed with the patent office on 2010-07-01 for low insertion force bga socket assembly.
This patent application is currently assigned to Cascade Microtech, Inc.. Invention is credited to Martin CAVEGN, Gregory D. SPANIER.
Application Number | 20100167559 12/640863 |
Document ID | / |
Family ID | 42025801 |
Filed Date | 2010-07-01 |
United States Patent
Application |
20100167559 |
Kind Code |
A1 |
CAVEGN; Martin ; et
al. |
July 1, 2010 |
LOW INSERTION FORCE BGA SOCKET ASSEMBLY
Abstract
A socket assembly includes a housing with a plurality of through
openings that extend between opposite surfaces of the housing.
First and second plurality of contact members are positioned in a
plurality of the through openings. The contact members each include
major beams and minor beams with proximal ends attached to a center
portion, and distal ends extending away from the center portion.
The major beams preferably have a length greater than the minor
beams. When the first circuit member is engaged with the socket
assembly the ball grid array displaces the distal ends of the major
beams to create a plurality of first and second forces. The first
plurality of forces generally oppose the second plurality of
forces. The first and second plurality of forces also generate an
engagement force that biases the first circuit member toward the
housing. The minor beams on the first and second plurality of
contact members do not contribute to the engagement force.
Inventors: |
CAVEGN; Martin; (Lino Lakes,
MN) ; SPANIER; Gregory D.; (Shakopee, MN) |
Correspondence
Address: |
FAEGRE & BENSON LLP;PATENT DOCKETING - INTELLECTUAL PROPERTY
2200 WELLS FARGO CENTER, 90 SOUTH SEVENTH STREET
MINNEAPOLIS
MN
55402-3901
US
|
Assignee: |
Cascade Microtech, Inc.
Beaverton
OR
|
Family ID: |
42025801 |
Appl. No.: |
12/640863 |
Filed: |
December 17, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61141477 |
Dec 30, 2008 |
|
|
|
Current U.S.
Class: |
439/65 |
Current CPC
Class: |
H05K 7/1069 20130101;
H05K 2201/10378 20130101; H05K 2201/10734 20130101 |
Class at
Publication: |
439/65 |
International
Class: |
H01R 12/00 20060101
H01R012/00 |
Claims
1. A socket assembly for electrically interconnecting a ball grid
array on a first circuit member with terminals on a second circuit
member, the socket assembly comprising: a housing comprising a
plurality of through openings that extend between opposite surfaces
of the housing; a first plurality of contact members positioned in
a plurality of the through openings, the first plurality of contact
members each comprising major beams and minor beams with proximal
ends attached to a center portion, and distal ends extending away
from the center portion, the major beams comprising a length
greater than the minor beams, wherein when the first circuit member
is engaged with the socket assembly the ball grid array displaces
the distal ends of the major beams of the first plurality of
contact members to create a plurality of first forces; a second
plurality of contact members positioned in a plurality of the
through openings, the second plurality of contact members each
comprising major beams and minor beams with proximal ends attached
to a center portion, and distal ends extending away from the center
portion, the major beams comprising a length greater than the minor
beams, wherein when the first circuit member is engaged with the
socket assembly the ball grid array displaces the distal ends of
the major beams of the second plurality of contact members to
create a plurality of second forces, wherein the first plurality of
forces generally oppose the second plurality of forces; and wherein
the first and second plurality of forces generate an engagement
force that biases the first circuit member toward the housing,
wherein the minor beams on the first and second plurality of
contact members do not contribute to the engagement force.
2. The socket assembly of claim 1 comprising: a third plurality of
contact members positioned in a plurality of the through openings,
wherein when the first circuit member is engaged with the socket
assembly the ball grid array displaces the distal ends of the major
beams of the third plurality of contact members to create a
plurality of third forces; and a fourth plurality of contact
members positioned in a plurality of the through openings, wherein
when the first circuit member is engaged with the socket assembly
the ball grid array on displaces the distal ends of the major beams
of the fourth plurality of contact members to create a plurality of
fourth forces, wherein the third plurality of forces generally
oppose the fourth plurality of forces.
3. The socket assembly of claim 1 wherein the first plurality of
forces are oriented generally toward the second plurality of
forces.
4. The socket assembly of claim 1 wherein the first plurality of
forces are oriented generally away from the second plurality of
forces.
5. The socket assembly of claim 1 wherein the first plurality of
forces are opposed by the minor beams of the first plurality of
contact members biased against the housing.
6. The socket assembly of claim 1 wherein the distal ends of the
minor beams do not engage the ball grid array.
7. The socket assembly of claim 1 wherein the distal ends of the
minor beams electrically couple with a distal surface of ball
members on the ball grid array.
8. The socket assembly of claim 1 wherein balls in the ball grid
array comprise a distal surface located beyond a widest
cross-section generally parallel to a lower surface of the first
circuit member, and the distal ends of the minor beams electrically
couple with the distal surface of the balls in the ball grid
array.
9. The socket assembly of claim 1 wherein the contact member
comprises a multi-layered structure.
10. The socket assembly of claim 1 wherein distal ends of the major
beams comprise an engagement feature adapted to engage with balls
in the ball grid array.
11. The socket assembly of claim 1 wherein distal ends of the major
beams comprise a recess adapted to engage with balls in the ball
grid array.
12. The socket assembly of claim 1 wherein the first and second
plurality of contact members are mechanically coupled with the
housing.
13. The socket assembly of claim 1 wherein side walls in the
through openings limit deflection of the major beams.
14. The socket assembly of claim 1 wherein the housing comprises a
plurality of layers.
15. The socket assembly of claim 1 wherein the housing comprises a
plurality of layers and at least one layer in the housing comprises
a circuit layer.
16. The socket assembly of claim 1 comprising a first circuit
member electrically coupled to the distal ends of the major beams
and a second circuit member electrically coupled to the center
portions of the contact members.
17. A socket assembly for electrically interconnecting a ball grid
array on a first circuit member with terminals on a second circuit
member, the socket assembly comprising: a housing comprising a
plurality of through openings that extend between a first surface
and a second surface of the housing; a first plurality of contact
members positioned in a plurality of the through openings, the
first plurality of contact members comprising major beams and minor
beams with proximal ends attached to a center portion, and distal
ends extending away from the center portion, the major beams
comprising a length greater than the minor beams, wherein when the
first circuit member is engaged with the socket assembly the ball
grid array on the first circuit member displaces the distal ends of
the major beams of the first plurality of contact members to create
a plurality of first forces; a second plurality of contact members
positioned in a plurality of the through openings, the second
plurality of contact members comprising major beams and minor beams
with proximal ends attached to a center portion, and distal ends
extending away from the center portion, the major beams comprising
a length greater than the minor beams, wherein when the first
circuit member is engaged with the socket assembly the ball grid
array on the first circuit member displaces the distal ends of the
major beams of the second plurality of contact members to create a
plurality of second forces, wherein the first plurality of forces
generally oppose the second plurality of forces; and an engagement
force that biases the first circuit member toward the housing
generated by the first and second plurality of forces, wherein the
minor beams on the first and second plurality of contact members
electrically couple with a distal surface of ball members on the
ball grid array.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority to Provisional Application
No. 61/141,477, filed Dec. 30, 2008, which is herein incorporated
by reference in its entirety.
FIELD OF THE INVENTION
[0002] The present invention is directed to a high performance
socket with a low insertion force for a BGA device.
BACKGROUND OF THE INVENTION
[0003] High performance integrated circuits are driving the demand
for high performance sockets, such as those disclosed herein and in
U.S. Pat. Nos. 6,247,938; 6,409,521; 6,939,143; 6,957,963;
6,830,460; 7,114,960; 7,121,839; and 7,160,119, which are hereby
incorporated by reference. As bus architectures become increasingly
complex the frequency of the signals is much higher and more
sensitive to changes in impedance. Next generation systems are
running at about 5 GHz. High performance sockets, such as those
identified above, have decreased pin pitch from about 1 millimeter
("mm") to from between about 0.4 mm and about 0.5 mm and pin count
is increasing.
BRIEF SUMMARY OF THE INVENTION
[0004] The present invention is directed to a high performance
socket for a BGA device with a low insertion force. The present
socket assembly is adapted to electrically couple a first circuit
member to contact members along a first side of a socket assembly,
and a second circuit member to the contact members along a second
side of the socket assembly.
[0005] The socket assembly includes a housing with a plurality of
through openings that extend between opposite surfaces of the
housing. A first plurality of contact members are positioned in a
plurality of the through openings. The first plurality of contact
members each include major beams and minor beams with proximal ends
attached to a center portion, and distal ends extending away from
the center portion. The major beams preferably have a length
greater than the minor beams. When the first circuit member is
engaged with the socket assembly the ball grid array displaces the
distal ends of the major beams of the first plurality of contact
members to create a plurality of first forces. A second plurality
of contact members are positioned in a plurality of the through
openings. The second plurality of contact members each include
major beams and minor beams. When the first circuit member is
engaged with the socket assembly the ball grid array displaces the
distal ends of the major beams of the second plurality of contact
members to create a plurality of second forces. The first plurality
of forces generally oppose the second plurality of forces. The
first and second plurality of forces also generate an engagement
force that biases the first circuit member toward the housing. The
minor beams on the first and second plurality of contact members do
not contribute to the engagement force.
[0006] The contact members can be arranged in a variety of
configurations to create one or more pairs of opposing forces. For
example, the socket assembly can optionally include a third
plurality of contact members that create a plurality of third
forces and a fourth plurality of contact members that create a
plurality of fourth forces, wherein the third plurality of forces
generally oppose the fourth plurality of forces.
[0007] The first plurality of forces can be oriented generally
toward or away from the second plurality of forces. In some
embodiments the first plurality of forces are opposed by the minor
beams. The distal ends of the minor beams may or may not
electrically couple with the ball grid array. The balls in the ball
grid array include a distal surface located beyond a widest
cross-section generally parallel to a lower surface of the first
circuit member. The distal ends of the minor beams preferably
electrically couple with the distal surface of the balls in the
ball grid array.
[0008] The contact member can be a homogeneous material or a
multi-layered structure. The first and second plurality of contact
members are preferably mechanically coupled with the housing. The
side walls in the through openings may limit deflection of the
major beams.
[0009] The distal ends of the major beams preferably include an
engagement feature adapted to engage with balls in the ball grid
array, such as for example a recess adapted to engage with balls in
the ball grid array.
[0010] The housing can be a single unitary structure or a plurality
of layers. In embodiments where the housing includes a plurality of
layers, at least one layer in the housing can be a circuit
layer.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0011] FIG. 1 is a side sectional view of a low-insertion force
socket assembly in accordance with an embodiment of the present
invention.
[0012] FIG. 2A is a side sectional view of the socket assembly of
FIG. 1 electrically coupled to first and second circuit
members.
[0013] FIG. 2B is a side sectional view of the socket assembly
generally as illustrated in FIG. 1 with the contact members rotated
180 degrees.
[0014] FIG. 3 is a schematic illustration of an array of contact
members in accordance with an embodiment of the present
invention.
[0015] FIG. 4 is a schematic illustration of an array of contact
members in accordance with an alternate embodiment of the present
invention.
[0016] FIG. 5 is a perspective view of an alternate low-insertion
force socket assembly in accordance with an embodiment of the
present invention.
[0017] FIG. 6 is a side sectional view of the socket assembly of
FIG. 5 electrically coupled to first and second circuit
members.
[0018] FIG. 7 is a side sectional view of a low-insertion force
socket assembly with a layered contact member in accordance with an
embodiment of the present invention.
[0019] FIG. 8 is a force vs. displacement graph of insertion force
for an exemplary socket assembly in accordance with an embodiment
of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] The present invention is directed to a high performance
socket for a BGA device with a low insertion force. Use of the
present socket assembly permits manufactures to install expensive
IC devices during system build, providing the opportunity to later
customize the system without stocking substitute circuit boards.
The use of the present socket assembly allows new IC devices to
replace initial release IC devices in the field (or at OEM) without
the need for disassembling the system or reworking the circuit
board. Trends towards lead-free electronics also increase the
attractiveness of the present socket assembly.
[0021] The present socket assembly accommodates wide range of pin
counts. In some embodiments, the pin counts are in the range of
about 1000-2500 I/O at 1.27 mm pitch or less, and more preferably a
pitch of about 0.8 millimeter or less, and most preferably a pitch
of about 0.5 millimeter or less. Such fine pitch interconnect
assemblies are especially useful for communications, wireless, and
memory devices.
[0022] FIG. 1 is a side sectional view of a low insertion force
socket assembly 50 in accordance with an embodiment of the present
invention. An array of contact members 52 are retained in housing
54 using a variety of techniques discussed below. The housing 54
can be constructed from a variety of dielectric or insulating
materials, such as for example, a polyethylene, lightweight
polyester composites, polyvinylchloride, Kapton.RTM. polyimide
film, or polytetrafluoroethelyne (PTFE).
[0023] The contact members 52 include a generally U-shaped
configuration with a pair of beams 56, 58 joined at a center
portion 60. Distal end 62 of the beam 56 includes an engagement
feature 64. In the illustrated embodiment, the engagement feature
64 is a protrusion and an associated recess 66 adapted to at least
partially engage with solder ball 72 on a circuit member 74 (see
FIG. 2A). Distal end 68 of the beam 58, on the other hand, includes
a tapered engagement surface 70. The contact members 52 can be any
conductive material, such as for example gold, copper, or BeCu.
[0024] As best illustrated in FIG. 2A, the pair of beams 56, 58 on
the contact member 52 preferably do not compressively engage the
solder balls 72 on first circuit member 74. Rather, a plurality of
contact members 52A, 52B are positioned so that a plurality of
major beams 56A, 56B generate opposing forces 78A, 78B on the
solder balls 72. The distal ends 68 of the minor beams 58
preferably contact distal surface 73 of the solder balls 70 located
below equator or widest cross-section 75 parallel to lower surface
80 of the first circuit member 74.
[0025] As the first circuit member 74 is brought into compressive
relationship with the housing 54, distal ends 62 of the contact
member 52 are displaced towards side walls 82 of the housing 54.
The sidewalls 82 may limit the displacement of the distal ends 62.
Since only the major beams 56 initially engage with the solder
balls 72, the insertion force 90 is preferably reduced by about 50%
relative to a two-beam capture system, while preserving the
redundant electrical path provided by the minor beams 58. The
insertion force 90 can be further reduced by decreasing the
cross-sectional area of the contact members 52, increasing the
length of the major beams 56, a combination thereof, or via other
means (e.g., using different materials).
[0026] As used in relation to forces acting on a BGA device in a
socket assembly, "opposing" or "opposed" refers to forces that act
against or counteract each other to some degree, and not to a
specific orientation or geometry of the forces. For example, in the
embodiment of FIG. 2, the forces 78 are not parallel or directly
opposed, although parallel and/or directly opposed forces are
encompassed by the various embodiments and the terms opposing and
opposed.
[0027] In the illustrated embodiment, the distal ends 62A, 62B,
62C, 62D (collectively "62") of the major beams 56A, 56B, 56C, 56D
(collectively "56"), respectively, engage the solder balls 72 in
region 77 between the equator or widest cross-section 75 and the
lower surface 80 of the first circuit member 74. Due to the curved
shape of the solder balls 72 in the region 77, vertical components
79A, 79B, 79C, 79D (i.e., generally perpendicular to the surface
80) of the forces 78A, 78B, 78C, 78D, respectively, are engagement
forces that biases the first circuit member 74 generally toward the
socket assembly 50.
[0028] In the embodiment of FIG. 2A, the distal ends 68 of the
minor beams 58 engage the solder balls 72 in the region 73 below
the equator or widest cross-section 75. Consequently, minor beams
58 do not contribute to the engagement forces 79 that bias the
circuit member 74 toward the socket assembly 50. The distal ends 68
of the minor beams 58 are also deflected by the solder balls 72. In
an alternate embodiment, the distal ends 68 are not deflected by
the solder balls 72. In the embodiment of FIGS. 5 and 6, the distal
ends 168 do not contact the solder balls 172. The distal ends 68,
168 of the minor beams 58, 158 are preferably configured to
minimize the insertion force 90.
[0029] By reconfiguring the distal end 62 of the major beams 56,
the angle of the forces 78 relative to the surface 80 of the first
circuit member 74 can be modified. For example, by increasing the
angle of the forces 78 relative to the surface 80, the vertical
components 79 are also increased, providing a greater engagement
force 79.
[0030] In the embodiment of FIG. 2A, the forces 78A, 78B generally
act toward the opposing forces 78C, 78D. FIG. 2B illustrates an
alternate embodiment with the contact members 52 rotated 180
degrees. Consequently, the opposing forces 78A, 78B act generally
away from the forces 78C, 78D.
[0031] The major beams 56 also restrict sideways movement of the
first circuit member 74 relative to the socket assembly 50. In the
illustrated embodiment, the minor beams 58A, 58B, 58C, 58D
(collectively "58") preferably contact the solder balls 72 to
provide a redundant electrical path. As used herein, the term
"circuit members" refers to, for example, a packaged integrated
circuit device, an unpackaged integrated circuit device, a printed
circuit board, a flexible circuit, a bare-die device, an organic or
inorganic substrate, a rigid circuit, or any other device capable
of carrying electrical current.
[0032] Center portion 60 preferably includes a distal end 92
configured to electrically couple with a second circuit member 94.
The distal end 92 can be configured to electrically couple with a
wide variety of circuit members, including for example a flexible
circuit, a ribbon connector, a cable, a printed circuit board, a
ball grid array (BGA), a land grid array (LGA), a plastic leaded
chip carrier (PLCC), a pin grid array (PGA), a small outline
integrated circuit (SOIC), a dual in-line package (DIP), a quad
flat package (QFP), a leadless chip carrier (LCC), a chip scale
package (CSP), or packaged or unpackaged integrated circuits. Each
distal end 92 may also include a solder ball that may be reflowed
to connect the socket assembly 54 to the second circuit member
94.
[0033] The housing 54 can be a unitary structure or a layered
structure. A layered housing permits internal features that would
normally be impossible to mold or machine. For large pin count
devices, the laminating process produces an inherently flat part
without requiring molds. Stiffening layers made of materials such
as BeCu, Cu, ceramic, or polymer filled ceramic can be added to
provide additional strength and to provide thermal stability during
solder reflow. A multi-layered housing can also include circuitry
layers. Power, grounding and/or decoupling capacitance can be added
between layers or between pins, and unique features such as
embedded IC devices or RF antennae can optionally be
incorporated.
[0034] In the illustrated embodiment, the housing 54 includes
center members 100 that helps position the contact members 52. The
center members 100 are preferably oriented along axis 102 of
openings 104 in the housing 54, permitting some movement of the
contact members 52 along the axis 102. In some embodiments, the
beams 56, 58 compressively engage with the center member 100 to
retain the contact members 52 in the housing 54. The contact
members 52 can be press fit into the housing 54. A post insertion
solder mask (as done on printed circuit boards and IC packages) can
also be added to improve solder deposit formation and wick
prevention. The center member 100 can also act as a stop for the
minor beams 58 when the major beams 56 are deflected by the first
circuit member 74.
[0035] The sizes and shape of the openings 104 and the center
member 100 can be adjusted so as to permit the contact member 52
some movement relative to the housing 54. Movement of the contact
member 52 along longitudinal axis 102 is of particular interest in
obtaining consistent and reliable electrical coupling with the
circuit members 74, 94.
[0036] Various alternate housings and contact member configurations
are disclosed in U.S. Pat. Nos. 6,830,460, 6,939,143, 6,957,963,
7,114,960, 7,121,839, 7,160,119, 7,297,003, 7,326,064, and
7,422,439, which are hereby incorporated by reference
[0037] FIGS. 3 and 4 illustrate various configurations of the
contact members 52 in accordance with embodiments of the present
invention. In the embodiment of FIG. 3, the contact members 52 are
arranged in diagonal rows 110A, 110B, 110C, 110D, etc.
(collectively, "110"). The contact members 52 are oriented in the
rows 110 so that the forces 78A, 78B, 78C, 78D, etc. (collectively
"78") alternate direction every other row 110. In the embodiment of
FIG. 4, the contact members 52 are arranged in four quadrants 120A,
120B, 120C, 120D. The forces 78A in quadrants 120A opposing the
forces 78C in 120C, while the forces 78B in quadrant 120B opposing
the forces 78D in quadrant 120D.
[0038] FIGS. 5 and 6 illustrate a perspective and side sectional
views of an alternate socket assembly 150 in accordance with an
alternate embodiment of the present invention. Circuit members 174
and 194 are not shown in FIG. 5 for clarity.
[0039] An array of contact members 152A, 152B, 152C, 152D, etc.
(collectively "152") are retained in housing 154 using any of the
techniques discussed herein. The contact member 152A includes a
generally U-shaped configuration with a pair of beams 156A, 158A
joined at a center portion 160A. Distal end 162A of the major beam
156A includes engagement feature 164A. In the illustrated
embodiment, the engagement feature 164A is a protrusion and an
associated recess 166A adapted to at least partially engage with a
solder ball 172 on circuit member 174 (see FIG. 6). Distal end 168A
of the beam 158A, on the other hand, is retained in the housing 154
and does not engage with the solder ball 172. Each of the contact
members 152 preferably has the features of contact member 152A.
[0040] As best illustrated in FIG. 5, the distal ends 162A, 162B,
162C, 162D, etc. (collectively "162") of the major beams 156A,
156B, 156C, 156D, etc. (collectively "156") are arranged to
generate generally opposing forces 178A, 178B, 178C, 178D, etc.
(collectively "178") The minor beams 158A, 158B, 158C, 158D, etc.
(collectively "158") preferably engage with center members 200 on
the housing 154 to oppose the forces 178. As discussed above, the
forces 178 are not necessarily parallel. The forces 178 preferably
bias the first circuit member 174 generally downward toward the
socket assembly 150.
[0041] FIG. 7 illustrates an alternate socket assembly 250 with a
multi-layers contact member 252. In the illustrated embodiment,
conductive member 254 is sandwiched between the polymeric layers
256, 258, leaving at least a portion of the side edges of the
conductive member 254 exposed. For example, the side edges of one
or more of the conductive members 254 may be exposed in the region
288 so as to be able to electrically couple with intermediate
circuit layer 286. Preferably, however, the conductive member 254
is substantially encapsulated or surrounded between the polymeric
layers 256, 258, except for the exposed first interface portion 260
and second interface portion 262.
[0042] The polymeric layers 256, 258 are preferably fused or bonded
such that they resemble a contiguous piece. The polymeric layers
256, 258 can also be mated with the use of adhesive, mechanical
fusion, melting of the base material or a seed layer, or even
deposition techniques used in semiconductor packaging or circuit
manufacturing processes. The polymeric layers 256, 258 provide
controlled or designed mechanical properties that can be modified
based upon the required geometries. The conductive member 254 can
be printed, etched, laser cut, stamped or molded either prior to
lamination or even after to create features or geometries that
provide the desired function. In one embodiment, the conductive
member 254 is formed directly on one of the polymeric layers 256,
258, such as for example by printing or etching. The opposing
polymeric layer is then laminated over the conductive member
254.
[0043] Portions 264 of the polymeric layers 256, 258 form
engagement features 266. In the illustrated embodiment, the
engagement feature 266 includes recesses 268 having a shape
generally corresponding a shape of solder ball 270 on the first
circuit member 272. A plurality of the contact members 254 are
arranged to create the opposing forces described in connection with
FIGS. 1 through 6. As the first circuit member 272 is pressed
towards the interconnect assembly 250, the engagement feature 266
flex outward in direction 274 until the solder ball 270 is engaged
with the recess 268.
[0044] Since the solder ball 270 is engaging with plastic portions
264, the insertion force can be relatively small. Additionally, the
plastic engagement feature 266 does not form a groove or otherwise
damage the solder ball 270 during insertion. The present composite
contacts permit an insertion process that places little or no
mechanical stress on the relatively thin conductive member 254.
[0045] Second interface portion 262 is configured to electrically
couple with contact pads 280 on the second circuit member 282. The
polymeric layers 256, 258 prevent solder around the second
interface portion 262 from wicking up into housing 284.
[0046] In the illustrated embodiment, housing 284 is a
multi-layered structure. Coupling layer 284 engages with coupling
feature 28 on the composite contact 252. In the illustrated
embodiment, the coupling feature 288 is a narrow region that
interlocks or couples with the coupling layer 286. Alternatively,
the coupling feature 288 can be a protrusion, an irregular or
asymmetrical edge, or a variety of other structures that are
adapted to engage with the housing 284.
[0047] Alignment layer 290 serves to position the second interface
portion 262 in a pre-determined location that corresponds with
contact pads 280 on the second circuit member 282. Stabilizing
layer 292 limits the deflection of the engagement feature 266 in
the direction 274. The layers 286, 290, 292 can be selectively
bonded or non-bonded to provide contiguous material or releasable
layers. As used herein, "bond" or "bonding" refers to, for example,
adhesive bonding, solvent bonding, ultrasonic welding, thermal
bonding, or any other techniques suitable for attaching adjacent
layers of the housing. In an alternate embodiment, a monolithic or
single layer housing can be used. The layers 286, 290, 292 can be
constructed from the same or multiple material types.
[0048] The housing 284 may be constructed of a dielectric material,
such as plastic. Suitable plastics include phenolics, polyesters,
and Ryton.RTM. available from Phillips Petroleum Company.
Alternatively, the housing 284 may be constructed from metal, such
as aluminum, with a non-conductive surface, such as an anodized
surface. For some applications, the metal housing may provide
additional shielding of the composite contacts. In an alternate
embodiment, the housing is grounded to the electrical system, thus
providing a controlled impedance environment. Some of the composite
contacts can be grounded by permitting them to contact an uncoated
surface of the metal housing.
[0049] The discrete layers 286, 290, 292 can be etched or ablated
and stacked without the need for expensive mold tooling. The layers
286, 290, 292 can create housing features that have a much larger
aspect ratio than typically possible with molding or machining The
layers 286, 290, 292 also permit the creation of internal features,
undercuts, or cavities that are difficult or typically not possible
to make using conventional molding or machining techniques,
referred to herein as a "non-moldable feature." The present
housings also permit stiffening layers, such as metal, ceramic, or
alternate filled resins, to be added to maintain flatness where a
molded or machined part might warp.
[0050] The layers 286, 290, 292 of the housing 284 can also
optionally include circuitry, such as disclosed in U.S. patent Ser.
No. 11/130,494 entitled Compliant Interconnect Assembly, filed May
17, 2005, which is hereby incorporated by reference. Power,
grounding and/or decoupling capacitance can be added to or between
the layers 286, 290, 292, or between pins, and unique features such
as embedded IC devices or RF antennae can optionally be
incorporated. In some cases, additional layers can be used to
assist with device insertion or removal, such as with ZIF or
stripper plate actuation mechanisms. Consequently, the interconnect
assembly 250 can be enhanced in ways not possible using
conventional molding or machining techniques.
[0051] In one embodiment, layer 286 is a circuit layer, such as for
example a ground plane or power plane. The circuit layer 286 can
optionally electrically couple to conductive member 254 proximate
the coupling feature 288. Selectively coupling the composite
contacts 252 to the circuit layer 286 permits the interconnect
assembly 250 to provide connectivity not readily available with
current connector structures.
[0052] The socket assemblies disclosed herein permit the creation
of high aspect ratio through holes and slots with internal cavities
having non-moldable features, to allow for contact flexure
clearance, on fine contact to contact spacing (pitch). The socket
assemblies provide the ability to press-fit the composite contacts
into lower layers to position, point and retain the composite
contacts and seal the interface to prevent solder or flux wicking
during reflow. A post insertion solder mask (as done on printed
circuit boards and IC packages) can also be added to improve solder
deposit formation and wick prevention.
[0053] The socket assemblies disclosed herein can optionally be
designed to receive multiple circuit members, such as the
replaceable chip modules disclosed in U.S. Pat. Nos. 5,913,687;
6,178,629; and 6,247,938, all of which are incorporated by
reference.
EXAMPLE
[0054] FIG. 8 is a force vs. displacement curve during insertion of
a BGA device into a socket assembly generally as illustrated in
FIGS. 1 and 2. The socket assembly has 208 contact members, each
0.1 millimeters thick. The contact members are constructed from a
metal alloy.
[0055] The contact members are arranged in opposing quadrants such
as illustrated in FIG. 4. The initial insertion force was about 20
grams per contact. The socket assembly was exposed to about 50
insertion cycles, after which the insertion force settled at about
16 grams per contact, or a total insertion force of about 3400
grams.
[0056] The location 300 on the graph illustrates the peak insertion
force at maximum ball diameter. The location 302 on the graph
illustrates the force exerted by the beams once the BGA device is
seat on the socket assembly.
[0057] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limit of that range and any other stated or intervening
value in that stated range is encompassed within the inventions.
The upper and lower limits of these smaller ranges which may
independently be included in the smaller ranges is also encompassed
within the inventions, subject to any specifically excluded limit
in the stated range. Where the stated range includes one or both of
the limits, ranges excluding either both of those included limits
are also included in the inventions.
[0058] Unless defined otherwise, all technical and scientific terms
used herein have the same meaning as commonly understood by one of
ordinary skill in the art to which these inventions belong.
Although any methods and materials similar or equivalent to those
described herein can also be used in the practice or testing of the
present inventions, the preferred methods and materials are now
described. All patents and publications mentioned herein, including
those cited in the Background of the application, are hereby
incorporated by reference to disclose and described the methods
and/or materials in connection with which the publications are
cited.
[0059] The publications discussed herein are provided solely for
their disclosure prior to the filing date of the present
application. Nothing herein is to be construed as an admission that
the present inventions are not entitled to antedate such
publication by virtue of prior invention. Further, the dates of
publication provided may be different from the actual publication
dates which may need to be independently confirmed.
[0060] Other embodiments of the invention are possible. Although
the description above contains many specificities, these should not
be construed as limiting the scope of the invention, but as merely
providing illustrations of some of the presently preferred
embodiments of this invention. It is also contemplated that various
combinations or sub-combinations of the specific features and
aspects of the embodiments may be made and still fall within the
scope of the inventions. It should be understood that various
features and aspects of the disclosed embodiments can be combined
with or substituted for one another in order to form varying modes
of the disclosed inventions. Thus, it is intended that the scope of
at least some of the present inventions herein disclosed should not
be limited by the particular disclosed embodiments described
above.
[0061] Thus the scope of this invention should be determined by the
appended claims and their legal equivalents. Therefore, it will be
appreciated that the scope of the present invention fully
encompasses other embodiments which may become obvious to those
skilled in the art, and that the scope of the present invention is
accordingly to be limited by nothing other than the appended
claims, in which reference to an element in the singular is not
intended to mean "one and only one" unless explicitly so stated,
but rather "one or more." All structural, chemical, and functional
equivalents to the elements of the above-described preferred
embodiment that are known to those of ordinary skill in the art are
expressly incorporated herein by reference and are intended to be
encompassed by the present claims. Moreover, it is not necessary
for a device or method to address each and every problem sought to
be solved by the present invention, for it to be encompassed by the
present claims. Furthermore, no element, component, or method step
in the present disclosure is intended to be dedicated to the public
regardless of whether the element, component, or method step is
explicitly recited in the claims.
* * * * *